XenAPI: VM diagnostics for v3 API

For V3 API the diagnostics will have the format defined at:
https://wiki.openstack.org/wiki/Nova_VM_Diagnostics

This will support backward compatability with the existing APIs

Part of the blueprint v3-diagnostics

DocImpact

Change-Id: I8377f86a97ca554028e4ca8c1c1af7fd5643cc2e
Merge commit 'refs/changes/53/58753/9' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/54/58754/11' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/55/58755/10' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/61/58861/10' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/53/60253/7' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch

Conflicts:
	nova/virt/xenapi/vm_utils.py
Merge commit 'refs/changes/08/60808/6' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/78/63778/1' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/38/66338/7' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch
Merge commit 'refs/changes/97/66597/3' of git://gold.eng.hq.xensource.com/git/github/openstack/nova into tmpbranch